Does a ban on something work?

New York City mayor Michael Bloomberg has today enacted a ban on super-sized sodas.
From a nutritional point of view, I have a number of disputes with the ban:
. Why only on super-sized portions?
. Why not ban diet sodas too, which have been shown to induce more sugar consumption later and are equally bad, if not worse, than regular sodas?
. Why a ban? Surely a tax on these diabetes and obesity inducers would be more prudent, more easily enforced, more effective...
From a political and business point of view, the more relevant question is what this will achieve.

First, it will achieve some positive PR to show that the mayor is doing something about obesity. Like many ill-fated policies in the past, the efficacy of a policy perhaps matters less than its mere existence.
Second, it may raise the debate about just why sugar water is so bad for people. It may also help to challenge portion sizes, reining in the proliferation of recent years.

But what of the bans likely impact?
I suspect there will be a movement towards diet sodas, which I cannot support and feel may end up being counter-productive in the fight against obesity and diabetes.
I suspect people will simply buy 2 smaller portions rather than the super-sized one.
Sugar is addictive. That's why the sodas are so dangerous for health. And as we all know, an addict will not let a ban get in the way of them getting a fix. whether that's an alternative supply (like the supermarket that can still sell large bottles of soda), an alternative product (diet), or another way around the ban (in this case buying more of the smaller sizes).
From a business point of view, expect to see heavy marketing to support one of these 3 strategies...2 for 1 deals on the smaller sizes, maybe? Supermarkets literally going "large" on their huge soda bottles. Expect too some, "we support the ban" type of advertising to improve drink suppliers credibility and reputation. Also note that the products these suppliers will tout will not necessarily be healthier options, simply ones that conform to the ban...not the same thing at all.

On a positive note, it is a start. Any more draconian measures would likely have been resisted even more. Time will tell whether this initiative has any positive impact at all. For the mayor there is unlikely to be an real scientific corroboration of the single impact of this ban - fortunately for him, life is more complicated than that.

History tells us that a ban rarely works. Pushing an addictive substance underground merely raises its price, and in some cases, its street cred. In this case, soda is not even being pushed undergroun. And diet soda is no methodone to regular soda's heroin (not that much evidence shows that to work either...)